Micro device integration into system substrate

ABSTRACT

Post-processing steps for integrating of micro devices into system (receiver) substrate or improving the performance of the micro devices after transfer. Post processing steps for additional structures such as reflective layers, fillers, black matrix or other layers may be used to improve the out coupling or confining of the generated LED light. Dielectric and metallic layers may be used to integrate an electro-optical thin film device into the system substrate with transferred micro devices. Color conversion layers may be integrated into the system substrate to create different outputs from the micro devices.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional under 35 U.S.C. § 121 and claimspriority under 35 U.S.C. § 120 to U.S. application Ser. No. 15/060,942(3USP1) filed on Mar. 4, 2016, which in turn is a continuation-in-partto U.S. application Ser. No. 15/002,662, filed Jan. 21, 2016 (3USPT),which claims priority to Canadian Application No. 2,890,398, filed May4, 2015 (129CAPL), Canadian Application No. 2,883,914, filed Mar. 4,2015 (128CAPL), Canadian Application No. 2,880,718, filed Jan. 28, 2015(127CAPL), Canadian Application No. 2,879,465, filed Jan. 23, 2015(125CAPL), and Canadian Application No. 2,879,627, filed Jan. 23, 2015(99CAPL), each of which is hereby incorporated by reference herein inits entirety. This application also claims priority to CanadianApplication No. 2,898,735, filed Jul. 29, 2015 (8CAP2) and CanadianApplication No. 2,887,186, filed Apr. 8, 2015 (128CAP2), each of whichis hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to the transferred micro device systemintegration on a receiver substrate. More specifically, the presentdisclosure relates to the post processing steps for enhancing theperformance of micro-devices after transferring into a receiversubstrate including the development of optical structure, theintegration of electro-optical thin film devices, the addition of colorconversion layers, and the proper patterning of devices on a donorsubstrate.

BRIEF SUMMARY

A few embodiments of this description are related to post-processingsteps for improving the performance of the micro devices. For example,in some embodiments, the micro device array may comprise micro lightemitting diodes (LEDs), Organic LEDs, sensors, solid state devices,integrated circuits, (micro-electro-mechanical systems) MEMS, and/orother electronic components. The receiving substrate may be, but is notno limited to, a printed circuit board (PCB), thin film transistorbackplane, integrated circuit substrate, or, in one case of opticalmicro devices such as LEDs, a component of a display, for example adriving circuitry backplane. In these embodiments, in addition tointerconnecting the micro devices, post processing steps for additionalstructure such as reflective layers, fillers, black matrix or otherlayers may be used to improve the out coupling of the generated LEDlight. In another example, dielectric and metallic layers may be used tointegrate an electro-optical thin film device into the system substratewith the transferred micro devices.

In one embodiment, the active area of the pixel (or sub-pixel) isextended to be larger than the micro device by using fillers, forexample, a dielectric. Here, the filler is patterned to define the pixelactive area. Herein a pixel (or sub-pixel) active area is defined as thearea that emits from the pixel (or sub-pixel), light produced by thelight emitting micro device (or devices) or in the case of a sensorserves to gather and direct received light to a light sensing microdevice of the pixel (or sub-pixel). In another embodiment reflectivelayers are used to confine the light within the active area.

According to one aspect, there is provided a method of integrated devicefabrication, the integrated device comprising a plurality of pixels eachcomprising at least one sub-pixel comprising a micro device integratedon a substrate, the method comprising: extending an active area of afirst sub-pixel to an area larger than an area of a first micro deviceof the first sub-pixel by patterning of a filler layer about the firstmicro device and between the first micro device and at least one secondmicro device.

One embodiment includes fabricating at least one reflective layercovering at least a portion of one side of the patterned filler layer,the reflective layer for confining at least a portion of incoming oroutgoing light within the active area of the sub-pixel.

In one case, the reflective layer is fabricated as an electrode of themicro device

In one case, the patterning of the filler layer further patterns thefiller layer about a further sub-pixel.

In another embodiment, the patterning of the filler layer further isperformed with a dielectric filler material.

According to another aspect, there is provided an integrated devicecomprising: a plurality of pixels each comprising at least one sub-pixelcomprising a micro device integrated on a substrate; and a patternedfiller layer formed about a first micro device of a first sub-pixel andbetween the first micro device and at least one second micro device, thepatterned filler layer extending an active area of the first sub-pixelto an area larger than an area of the first micro device.

In one case, the integrated device further comprises: at least onereflective layer covering at least a portion of one side of thepatterned filler layer, the reflective layer for confining at least aportion of incoming or outgoing light to the active area of the firstsub-pixel.

In one case, the reflective layer is an electrode of the micro device.

In one embodiment, the patterned filler layer is formed about a furthersub-pixel.

According to a further aspect there is provided a method of integrateddevice fabrication, the device comprising a plurality of pixels eachcomprising at least one sub-pixel comprising a micro device integratedon a substrate, the method comprising: integrating at least one microdevice into a receiver substrate; and subsequently to the integration ofthe at least one micro device, integrating at least one thin-filmelectro-optical device into the receiver substrate.

In some embodiments integrating the at least one thin-filmelectro-optical device comprises forming an optical path for the microdevice through all or some layers of the at least one electro-opticaldevice.

In some embodiments integrating the at least one thin-filmelectro-optical device is such that an optical path for the micro deviceis through a surface or area of the integrated device other than asurface or area of the electro-optical device.

Some embodiments further comprise fabricating an electrode of thethin-film electro-optical device, the electrode of the thin-filmelectro-optical device defining an active area of at least one of apixel and a sub-pixel.

Some embodiments further comprise fabricating an electrode which servesas a shared electrode of both the thin-film electro-optical device andthe light emitting micro device.

In one embodiment, one of the micro device electrodes can serve as thereflective layer.

In another embodiment, the active area can consist of a few sub-pixelsor pixels.

The active area can be larger, smaller, or the same size as the pixel(or sub-pixel) area.

In this description pixel active area and sub-pixel active area are usedinterchangeably. However, it is clear to one skilled in the art that thepixel and/or sub-pixel can be used in all the embodiments describedhere.

In another embodiment, thin film electro-optical devices are depositedonto the receiver substrate after the micro devices are integrated intothe receiver substrate.

In one embodiment, an optical path is developed for the micro device toemits (or absorb) light through all or some layers of theelectro-optical device.

In another embodiment, the optical path for the micro device is notthrough all or some layers of the electro-optical device.

In one embodiment, the electro-optical device is a thin film device.

In another embodiment, the electrode of the electro-optical device isused to define the active area of the pixel (or sub-pixel).

In another embodiment, at least one of the electro-optical deviceelectrodes is shared with the micro-device electrode.

In one embodiment, color conversion material covers the surface andsurrounds partially (or fully) the body of the micro device.

In one embodiment, the bank structure separates the color conversionmaterials.

In another embodiment, color conversion material covers the surface(and/or partially or fully the body of) the active area.

In one embodiment, the micro devices on donor substrate are patterned tomatch the array structure in the receiver (system) substrate. In thiscase, all the devices in part (or all) of the donor substrate aretransferred to the receiver substrate.

In another embodiment, VIAs are created in the donor substrate to couplethe micro devices on the donor substrate with the receiver substrate.

In another embodiment, the donor substrate has more than one microdevice type and at least in one direction the pattern of the microdevice types on the donor substrate matches partially or fully thepattern of the corresponding areas (or pads) on the system substrate.

In another embodiment, the donor substrate has more than one microdevice type and at least in one direction the pitch between differentmicro devices in donor substrate is a multiple of the pitch of thecorresponding areas (or pads) on the system substrate.

In another embodiment, the donor substrate has more than one microdevice type. At least in one direction, the pitch between two differentmicro devices matches the pitch of the corresponding areas (or pads) onthe receiver (or system) substrate.

In one embodiment, the pattern of different micro device types on thedonor substrate creates a two dimensional array of each type where thepitch between each array of different types matches the pitch of thecorresponding areas on the system substrate.

In another embodiment, the pattern of different micro device types onthe donor substrate creates a one dimensional array where the pitch ofthe arrays matches the pitch of the corresponding areas (or pads) on thesystem substrate.

The foregoing and additional aspects and embodiments of the presentdisclosure will be apparent to those of ordinary skill in the art inview of the detailed description of various embodiments and/or aspects,which is made with reference to the drawings, a brief description ofwhich is provided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the disclosure will becomeapparent upon reading the following detailed description and uponreference to the drawings.

FIG. 1 shows a receiver substrate with contact pads, and an array oftransferred micro-devices attached to the receiver substrate.

FIG. 2A shows a receiver substrate with contact pads, an array oftransferred micro-devices attached to the receiver substrate, andconformal dielectric and reflective layers on top.

FIG. 2B shows a receiver substrate with contact pads, an array oftransferred micro-devices attached to the receiver substrate, andpatterned conformal dielectric and reflective layers.

FIG. 2C shows a receiver substrate with contact pads, an array oftransferred micro-devices attached to the receiver substrate, patternedconformal dielectric and reflective layers, and a black matrix layerformed between adjacent micro-devices.

FIG. 3A shows a receiver substrate with contact pads, an array oftransferred micro-devices attached to the receiver substrate, patternedconformal dielectric and reflective layers, a black matrix layer, and atransparent conductive layer deposited on the substrate.

FIG. 3B shows a receiver substrate with an integrated array oftransferred micro-devices attached to the receiver substrate and opticalreflective components for light outcoupling enhancement.

FIG. 3C shows a receiver substrate with an integrated array oftransferred micro-devices attached to the receiver substrate and concavecontact pads for light outcoupling enhancement.

FIG. 3D shows a receiver substrate with an integrated array oftransferred micro-devices attached to the receiver substrate in a bottomemission configuration.

FIG. 3E shows a receiver substrate with an integrated array oftransferred micro-devices attached to the receiver substrate.

FIG. 4A shows a receiver substrate with transferred micro-devices, aconformal dielectric layer, and a connected reflective layer.

FIG. 4B shows a receiver substrate with transferred micro-devices,conformal dielectric layer, connected reflective layer, and atransparent conductive layer deposited on the substrate.

FIG. 5 shows a receiver substrate with transferred micro-devices and apatterned filler which defines the pixels (or sub-pixels).

FIG. 6A shows a pixelated filler structure covering all sub-pixels in atleast one pixel (for example covering both sub-pixels for a pixel madeof two sub-pixels).

FIG. 6B shows a pixel made of two sub-pixels, a filler layer which ispatterned to define the pixel, and patterned conformal dielectric andreflective layers around the pixel.

FIG. 6C shows a pixel made of two sub-pixels, a filler layer which ispatterned to define the pixel, patterned conformal dielectric andreflective layers around the pixel, and a black matrix layer wrappedaround the pixel.

FIG. 6D shows a pixel made of two sub-pixels, a filler layer which ispatterned to define the pixel, patterned conformal dielectric andreflective layers around the pixel, a black matrix layer wrapped aroundthe pixel, and a transparent conductive layer deposited on thesubstrate.

FIG. 6E shows a pixel made of two sub-pixels with reflective opticalcomponents on the receiver substrate for better light outcoupling.

FIG. 6F shows a pixel made of two sub-pixels with concave contact padson the receiver substrate.

FIG. 6G shows a pixel made of two sub-pixels with a bottom emissionconfiguration.

FIG. 6H shows a pixel made of two sub-pixels with a bottom emissionconfiguration, a common top electrode, and side reflectors.

FIG. 7 shows a receiver substrate with two contact pads.

FIG. 8 shows a receiver substrate with a transferred micro device bondedto one of the contact pads.

FIG. 9 shows the integration of a transferred micro-device with anelectro-optical thin film device in a hybrid structure.

FIG. 10 shows another example of an integration of a transferredmicro-device with an electro-optical thin film device in a hybridstructure.

FIG. 11 shows an example of the integration of a transferredmicro-device with an electro-optical thin film device in a hybridstructure with a common top electrode.

FIG. 12 shows an embodiment for the integration of a transferredmicro-device with an electro-optical thin film device in a dual surfacehybrid structure with both top and bottom transparent electrodes.

FIG. 13A shows another embodiment for a system substrate and anintegrated micro device with thin film electro-optical device.

FIG. 13B shows another embodiment of a system substrate and anintegrated micro device with a thin film electro-optical device.

FIG. 14A shows a modified embodiment of a system substrate and anintegrated micro device with two thin film electro-optical devices.

FIG. 14B shows an example of a system substrate and an integrated microdevice with two thin film electro-optical devices and a reflective layeron the receiver substrate.

FIG. 15 illustrates a cross section of a system substrate and a microdevice substrate.

FIG. 16 shows the alignment step for a system substrate and a microdevice substrate in a transfer process.

FIG. 17 shows the bonding step for a system substrate and a micro devicesubstrate in a transfer process.

FIG. 18 shows the micro device substrate removal step for a systemsubstrate and a micro device substrate in a transfer process.

FIG. 19 shows the sacrificial layer removal step for a system substrateand a micro device substrate in a transfer process.

FIG. 20 shows the common electrode formation step for a system substrateand a micro device substrate in a transfer process.

FIG. 21 is a cross section of a micro device substrate with a fillerlayer(s).

FIG. 22 is a cross section of a micro device substrate covered with asupport layer.

FIG. 23 shows the micro device substrate removal step for a micro devicesubstrate in a transfer process.

FIG. 24A shows the sacrificial/buffer layer removal step for a microdevice substrate in a transfer process. A system substrate with contactpads is shown as well.

FIG. 24B shows the exposed micro devices after removal of thesacrificial/buffer layer.

FIG. 25 shows the bonding step for a system substrate and a micro devicesubstrate in a transfer process.

FIG. 26A shows the supporting layer removal step for a micro devicesubstrate in a transfer process. A system substrate with contact padsand transferred micro devices is shown as well.

FIG. 26B shows the exposed micro devices after removal of the supportinglayer and the filler layer.

FIG. 27 is a cross section of a micro device substrate covered with afiller layer.

FIG. 28A is a cross section of a micro device substrate with via holesin the substrate and the sacrificial layer.

FIG. 28B is the cross section shown in FIG. 28A, after removal of thebuffer layer.

FIG. 29 is a cross section of a micro device substrate with via holes inthe substrate and the sacrificial layer covered by an insulating layer.

FIG. 30 is a cross section of a micro device substrate with a conductivelayer filled via holes in the substrate and the sacrificial layer.

FIG. 31 is a cross section of a micro device substrate with a common topelectrode.

FIG. 32 is a cross section of an integrated system substrate with acommon top electrode.

FIG. 33A shows a two dimensional arrangement of micro devices in a donorsubstrate.

FIG. 33B is a cross section of a system substrate and a micro devicesubstrate.

FIG. 34 is a cross section of a bonded system substrate and micro devicesubstrate.

FIG. 35 shows the laser lift-off step for a micro device substrate in atransfer process.

FIG. 36 is a cross section of a system substrate and a micro devicesubstrate after the selective transfer process.

FIG. 37 shows an integrated system substrate with a common topelectrode.

FIG. 38A is a cross section of a micro device substrate with microdevices having different heights.

FIG. 38B is the cross section shown in FIG. 38A after the buffer layerhas been patterned.

FIG. 39 is a cross section of a micro device substrate with a fillerlayer.

FIG. 40 shows the alignment step for a system substrate with gripmechanisms and a micro device substrate in a transfer process.

FIG. 41A shows a two dimensional arrangement of micro devices in a donorsubstrate.

FIG. 41B is a cross section of a system substrate and a micro devicesubstrate with different pitches.

FIG. 42 shows the selective micro device transfer process for a systemsubstrate and a micro device substrate with different pitches.

FIG. 43 is a cross section of a system substrate and a micro devicesubstrate with different pitches.

FIG. 44 shows the selective micro device transfer process for a systemsubstrate and a micro device substrate with different pitches.

FIG. 45 shows an integrated micro device substrate.

FIG. 46A shows the transfer process of micro devices to a systemsubstrate with a planarization layer, a common top electrode, bankstructures, and color conversion elements.

FIG. 46B shows the structure of FIG. 46A with the addition of a commonelectrode formed on the planarization layer.

FIG. 47 shows a structure with color conversion for defining the colorof pixels.

FIG. 48 shows a structure with conformal common electrode and colorconversion separated by a bank layer.

FIG. 49 shows a structure with conformal color conversion separated by abank layer.

FIG. 50 shows a structure with color conversion elements on the commonelectrode without the bank layer.

FIG. 51 shows a structure with conformal common electrode and colorconversion.

FIG. 52 shows a structure with conformal color conversion elementsformed directly on the micro devices.

FIG. 53A shows a structure with color conversion for defining pixelcolor, a planarization layer, and a common transparent electrode.

FIG. 53B shows the structure of FIG. 53A after forming the encapsulationlayer.

FIG. 54A shows a structure with color conversion for defining pixelcolor and a separate substrate for encapsulation.

FIG. 54B shows the structure of FIG. 54B after the substrate coated withthe encapsulation layer is bonded to the integrated system substrate.

FIG. 55A shows a structure with a system substrate with contact pads,and a separate donor substrate with micro devices.

FIG. 55B shows the structure of FIG. 55A after transfer of the microdevices to the system substrate.

FIG. 55C shows the structure of FIG. 55B after post processing todeposit a common electrode and color conversion layers.

While the present disclosure is susceptible to various modifications andalternative forms, specific embodiments or implementations have beenshown by way of example in the drawings and will be described in detailherein. It should be understood, however, that the disclosure is notintended to be limited to the particular forms disclosed. Rather, thedisclosure is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of an invention as defined by theappended claims.

DETAILED DESCRIPTION

The process of developing a system based on micro devices consists ofpre-processing the devices on a donor substrate (or a temporarysubstrate), transferring the micro devices from the donor substrate tothe receiver substrate, and post processing to enable devicefunctionality. The pre-processing step may include patterning and addingbonding elements. The transfer process may involve bonding of apre-selected array of micro devices to the receiver substrate followedby removing the donor substrate. Several different selective transferprocesses have already been developed for micro devices. After theintegration of the micro devices into the receiving substrate,additional post processes may be performed to make required functionalconnections.

In this disclosure, “emissive device” is used to describe differentintegration and post processing methods. However, it is clear for oneskilled in the art that other devices such as sensors can be used inthese embodiments. For example, in case of sensor micro devices, theoptical path will be similar to emissive micro devices but in reversedirection.

Some embodiments of this disclosure are related to post-processing stepsfor improving the performance of the micro devices. For example, in someembodiments, the micro device array may comprise micro light emittingdiodes (LEDs), Organic LEDs, sensors, solid state devices, integratedcircuits, MEMS (micro-electro-mechanical systems), and/or otherelectronic components. The receiving substrate may be, but is not nolimited to, a printed circuit board (PCB), thin film transistorbackplane, integrated circuit substrate, or, in one case of opticalmicro devices such as LEDs, a component of a display, for example adriving circuitry backplane. In these embodiments, in addition tointerconnecting the micro devices, post processing steps for additionalstructure such as reflective layers, fillers, black matrix or otherlayers may be used to improve the out coupling of the generated LEDlight. In another example, dielectric and metallic layers may be used tointegrate an electro-optical thin film device into the system substratewith the transferred micro devices.

In one embodiment, the active area of the pixel (or sub-pixel) isextended to be larger than the micro device by using fillers (ordielectric). Here, the filler is patterned to define the pixel's activearea (the active area is the area that emits light or is absorbing inputlight). In another embodiment, reflective layers are used to confine thelight within the active area.

In one embodiment, the reflective layer can be one of the micro deviceelectrodes.

In another embodiment, the active area can consist of a few sub-pixelsor pixels.

The active area can be larger, smaller, or the same size as the pixel(sub-pixel) area.

In another embodiment, thin film electro-optical devices are depositedinto the receiver substrate after the micro devices are integrated intothe receiver substrate.

In one embodiment, an optical path is developed for the micro device toemit (or absorb) light through all or some layers of the electro-opticaldevice.

In another embodiment, the optical path for the micro device is notthrough all or some layers of the optoelectronic device.

In one embodiment, the optoelectronic device is a thin film device.

In another embodiment, the electrode of the electro-optical device isused to define the active area of the pixel (or sub-pixel).

In another embodiment, at least one of the electro-optical deviceelectrodes is shared with the micro-device electrode.

In one embodiment color conversion material covers the surface andsurrounds partially (or fully) the body of the micro device.

In one embodiment, the bank structure separates the color conversionmaterials.

In another embodiment color conversion material covers the surface(and/or partially or fully the body of) the active area.

In one embodiment, the micro devices on donor substrate are patterned tomatch the array structure in the receiver (system) substrate. In thiscase, all the devices in part (or all) of the donor substrate aretransferred to the receiver substrate.

In another embodiment, VIAs are created in the donor substrate to couplethe micro devices on the donor substrate with the receiver substrate.

In another embodiment, the donor substrate has more than one microdevice types and at least in one direction the pattern of the microdevice types on the donor substrate matches partially or fully thepattern of the corresponding areas (or pads) on the system substrate.

In another embodiment, the donor substrate has more than one microdevice types and at least in one direction the pitch between differentmicro devices in donor substrate is a multiple of the pitch of thecorresponding area (or pads) on the system substrate.

In another embodiment, the donor substrate has more than one microdevice type. At least in one direction, the pitch between two differentmicro devices matches the pitch of the corresponding areas (or pads) onthe receiver (or system) substrate.

In one embodiment, the pattern of different micro device types on thedonor substrate creates a two dimensional array of each type where thepitch between each array of different types matches the pitch of thecorresponding areas on the system substrate.

In another embodiment, the pattern of different micro device types onthe donor substrate creates a one dimensional array where the pitch ofthe arrays matches the pitch of the corresponding areas (or pads) on thesystem substrate.

FIG. 1 shows a receiver substrate 100, contact pads 101 a and 101 b, andmicro devices 102 a and 102 b, being in an array attached to thereceiver substrate 100. Contact pads 101 where micro devices 102 havebeen transferred, are located in an array on receiver substrate 100.Micro devices 102 are transferred from a donor substrate and bonded tothe contact pads 101. Micro devices 102 can be any micro device that maytypically be manufactured in planar batches including but not limited toLEDs, OLEDs, sensors, solid state devices, integrated circuits, MEMS,and/or other electronic components.

As depicted in FIG. 2A, in one embodiment where the micro devices 102are micro LEDs, a conformal dielectric layer 201 and a reflective layer202 may be formed over the bonded micro LEDs. In some embodiments, theconformal dielectric layer 201 is approximately 0.1-1 μm thick and itmay be deposited by any of a number of different thin film depositiontechniques. The conformal dielectric layer 201 isolates the micro LEDsidewalls from the reflective layer 202. In addition, the dielectriclayer 201 passivates and protects the micro LED sidewalls. The conformaldielectric layer 201 may also cover the top surface of the receiversubstrate 100 between adjacent micro LED devices 102 a and 102 b. Theconformal reflective layer 202 may be deposited over the dielectriclayer 201. The reflective layer 202 may be a single layer or made up ofmultiple layers. A variety of conductive materials may be used as thereflective layer 202. In some embodiments, the conformal reflectivelayer 202 may be a metallic bilayer with a total thickness up to 0.5 μm.

Referring to FIG. 2B, the dielectric layer 201 and reflective layer 202may then be patterned by using for example lithographic patterning andetching to partially expose the top surface of micro LEDs 102. In oneembodiment where the micro LEDs are integrated into a backplane of adisplay system, referring also to FIG. 2C, a black matrix 203 may beformed between adjacent micro LEDs 102 and on the reflective layer 202to reduce the reflection of the ambient light. In one example the blackmatrix 203 may be a layer of resins such as polyimide or polyacrylic inwhich particles of black pigment such as carbon black have beendispersed. In some embodiments, the thickness of the black matrix 203may be 0.01-2 μm. This layer may be patterned and etched so as to exposethe top surface of the micro LEDs 102 as shown in FIG. 2C. Optionally,the thickness of the black matrix 203 may be engineered to planarize theintegrated substrate 100. In another embodiment, a planarization layerwhich may be made of organic insulating material is formed and patternedto planarize the backplane substrate.

Referring to FIG. 3A, a transparent conductive layer 301 may beconformally deposited on the substrate, covering the black matrix 203and the top surface of micro LEDs 102. In some embodiments, thetransparent electrode 301 may be 0.1-1 um thick layers of oxides,including but not limited to indium tin oxide (ITO) and Aluminum dopedZinc Oxide. In a case where the integrated assembly is a displaystructure, the transparent electrode 301 may be the common electrode ofthe micro LED devices 102.

Optionally, the reflective layer 202 may be used as a conductivitybooster for the transparent electrode 301. In this case, part of thereflective layer may not be covered with black matrix 203, or otherplanarization layers, so that the transparent electrode layer 301 mayconnect to the reflective layer 202.

In another embodiment shown in FIG. 3B, a reflective or other type ofoptical component 302 may be formed on the substrate 100 to enhanceoutcoupling of light produced by micro devices 102 a and 102 b. Thecommon contact 301 is transparent to allow light output through thislayer. These structures may be referred as top emission structures.

Referring to FIG. 3C, the contact pad 101 may be formed to have aconcave or other shaped structure to enhance the outcoupling of lightproduced by microdevices 102. The contact pad form is not limited to theconcave form and may have other forms depending on the micro devicelight emission characteristics.

In an embodiment, referring to FIG. 3D, the structure is designed tooutput light from the substrate. In these bottom emission structures,the substrate 100 may be transparent and the common electrode 303 isdesigned to be reflective for better light extraction.

In another embodiment shown in FIG. 3E, the reflective layer 202 may beextended to cover the micro devices and act as the common top electrodeas well.

Referring to FIG. 4A, in another embodiment, the dielectric layer 201may be deposited and patterned before forming the reflective layer 202.As shown in FIG. 4, this may allow a direct contact between micro LEDs102 and the reflective layer 202 which may be used as a common topcontact for the micro devices 102. Black matrix 203 or alternatively aplanarization layer may be used.

Referring to FIG. 4B, in other embodiments, a common transparentelectrode 301 or/and other optical layers may be deposited on top of thesubstrate 100 to enhance conductivity and/or light out coupling.

One of the main challenges with micro optoelectronic devices is theempty space between adjacent micro devices. Display systems with thisstructural characteristic may create an image artifact called the“screen door effect.” In one embodiment, the micro device sizes may beoptically extended to be the same or larger than the micro device size.In one embodiment shown in FIG. 5, after transferring the array of microdevices 102 from the donor to the receiver substrate 100, transparentfiller 501 is deposited and patterned to define the pixel (orsub-pixel). In one example, the filler size can be the smaller or themaximum size possible in a pixel (or sub-pixel) area. In anotherexample, the filler size may be larger than the pixel or sup-pixel area.The filler may have a different or a similar shape as the pixel area onthe system substrate. The processes illustrated in FIG. 3 and FIG. 4 maythen be applied to improve the light extraction from the micro devices.

Referring to FIG. 6A, in an embodiment where the pixel 601 is made oftwo sub-pixels 601 a and 601 b, the filler 501 is patterned to definethe active area of the pixel 601 (active area being defined as the areafrom which the display emits light). Here, the active area can besmaller, larger, or the same size as the pixel (or sub-pixel) area. Asshown in FIG. 6B, FIG. 6C, and FIG. 6D processes mentioned in FIG. 2 andFIG. 3 may be applied. This configuration manages the discoloration atthe edges due to the separation between sub-pixels

Referring to FIG. 6B, a dielectric layer 201 and a reflective layer 202may be formed around over pixel 601.

Referring also to FIG. 6C, a black matrix 203 may be formed betweenadjacent pixels and around each pixel to reduce the reflection of theambient light.

Referring to FIG. 6D, a transparent conductive layer 301 may bedeposited on the substrate, covering the black matrix 203 and the topsurface of micro LEDs 601 a and 601 b.

In another embodiment shown in FIG. 6E, reflective or other opticalcomponent 602 may be formed on the substrate 100 to enhance outcouplingof light produced by micro devices 601 a and 601 b. The common contact301 is transparent for the light to output through this layer. Thesestructures may be referred to as top emission structures.

Referring to FIG. 6F, the contact pad 101 may be formed to have aconcave structure to enhance the outcoupling of light produced by microdevices 601. The contact pad form is not limited to the concave form andmay have other forms depending on the micro device light emissioncharacteristics.

Referring to FIG. 6G, in another embodiment, the structure is designedto output light from the substrate. In these bottom emission structures,the substrate 100 may be transparent and the common electrode 303 isdesigned to be reflective for better light extraction.

In another embodiment shown in FIG. 6H, the reflective layer 202 may beextended to cover the micro devices and act as the common top electrodeas well.

In other embodiments, the aforementioned pixel definition structure cancover more than one pixel (or sub-pixel).

In another case, a reflective layer or the contact pads on the receivingsubstrate may be used to cover the receiving substrate and create areflective area before transferring the micro devices for better lightout coupling.

In all aforementioned embodiments, the reflective layer can also beopaque. In addition, the reflective layers can be used as one of themicro device electrodes or as one of the system substrate connections(electrode, signal, or power line). In another embodiment, thereflective layer can be used as a touch electrode. The reflective layerscan be patterned to act as a touch screen electrode. In one case, theycan be patterned in vertical and horizontal directions to form the touchscreen crossing electrode. In this case, one can use a dielectricbetween vertical and horizontal traces.

Hybrid Structures

In another embodiment, a thin film electro-optical device is integratedinto the receiver substrate after the micro device arrays have beentransferred to the receiver substrate.

FIG. 7 shows a receiver substrate 100 and contact pads 702 upon whichthe micro device arrays are transferred and into which the thin filmelectro-optical device is integrated in a number of hybrid structureembodiments.

Referring to FIG. 8, micro device 801 may be transferred and bonded tothe bonding pad 702 a of the receiver substrate 100. In one case, asshown in FIG. 9 a dielectric layer 901 is formed over the substrate 100to cover the exposed electrodes and conductive layers. Lithography andetching may be used to pattern the dielectric layer 901. Conductivelayer 902 is then deposited and patterned to form the bottom electrodeof the thin film electro-optical device 904. If there is no risk ofunwanted coupling between bottom electrode 902 and other conductivelayers in the receiver substrate, the dielectric layer 901 may beeliminated. However, this dielectric layer can act as planarizationlayer as well to offer better fabrication of electro-optical devices904.

Still referring to FIG. 9, a bank layer 903 is deposited on thesubstrate 100 to cover the edges of the electrode 902 and the microdevice 801. Thin film electro-optical device 904 is then formed overthis structure. Organic LED (OLED) devices are an example of such a thinfilm electro-optical device which may be formed using differenttechniques such as but not limited to shadow mask, lithography, andprinting patterning. Finally, the top electrode 905 of theelectro-optical thin film device 904 is deposited and patterned ifneeded.

In an embodiment where the micro devices' 801 thickness is significantlyhigh, cracks or other structural problems may occur within the bottomelectrode 902. In these embodiments, a planarization layer may be usedin conjunction with or without the dielectric layer 901 to address thisissue.

In another embodiment shown in FIG. 10, the micro device 801 can have adevice electrode 1001. This electrode can be common between other microdevices in the system substrate. In this case, the planarization layer(if present) and/or bank layer 903 covers the electrode 1001 to avoidany shorts between the electro-optical device 904 and device electrode1001.

Referring to FIG. 11, in one embodiment, top electrode 905 of the thinfilm electro-optical device 904 may be connected to the micro device 801through an opening in the planarization layer. In this case, theelectro-optical device 904 may be formed selectively so that it is notcovering this opening.

In another case, the bottom electrode of the micro device can be sharedbetween the thin film electro-optical device and the transferred microdevice.

Referring to FIG. 12, in another example, the bottom electrode 902 ofthe thin film electro-optical device 904 can be expanded over the microdevice 801. In case the micro device 801 needs to have a transparentpath to the outside through its top electrode, the bottom electrode 902(if not transparent) needs to have an opening over the micro device (forexample as shown in FIG. 13A in association with another embodiment). Inthis case, the opening can be covered by the bank layer 903 as well. Theopening is not limited to the specific structure illustrated in FIG. 12and can be developed with different methods.

Still referring to FIG. 12, the micro device 801 can have a transparentpath through the substrate 100 if electrode 702 is transparent. In acase where a transparent path is required through its top electrode,either the bottom electrode 902 and the micro device top electrode needto be transparent or there needs to be opening in the bottom electrode902. FIG. 13A shows a layout structure where the bottom electrode 902has an opening to allow a transparent path through the top electrode905. There can be an opening 1301 in the bank layer 903 for the commontop electrode 905. If there is no common top electrode 905 and if thebank layer 903 is transparent, the opening in the bank layer 903 is notneeded. In some embodiments, if the top electrode 905 is also opaque, anopening in the top electrode 905 is also needed for top emission.

Referring to FIG. 13B, in another embodiment, to provide a transparentpath for the micro device 801, the bottom electrode 902 does not coverthe micro device 801. There can be an opening 1301 in the bank layer 903for a common top electrode. If there is no common electrode and the banklayer 903 is transparent, the opening in the bank layer 903 is notneeded.

In another case, the contact of the thin film electro-optical device canbe extended to act as reflective layer. As can be seen in FIG. 14A, thetwo side-by-side pixels can act to confine the light generated by themicro device 801 in the pixel. In another embodiment shown in FIG. 14B,the reflective layer 1401 on the surface of the substrate 100 canreflect more of the lights toward the top electrode 905. As a result,the out coupling of the light generated by the micro device 801 isenhanced. In this case, the best practice is either to make both top andbottom electrode of the thin film electro-optical device transparent, ormake openings if these electrodes are opaque.

In another embodiment, the thin film electro-optical devices and microdevices can be on two opposite sides of the system substrate. In thiscase, the system substrate circuitry can either be on one side of thesystem substrate and connected to the other side through contact holesor, the circuits can be on both sides of the system substrate.

In another case, the micro device can be on one system substrate and thethin film electro-optical device on another system substrate. These twosubstrates may then be bonded together. In this case, the circuit can beon one of the system substrates or on both substrates. INTEGRATION

This document also discloses various methods for the integration of amonolithic array of micro devices into a system substrate or selectivetransferring of an array of micro devices to a system substrate. Here,the proposed processes are divided into two categories. In the firstcategory, the pitch of the bonding pads on the system substrate is thesame as the pitch of the bonding pads of the micro devices. In thesecond category, bonding pads on the system substrate have a largerpitch compared to that of the micro devices. For the first category,three different schemes of integration or transfer are presented

1. Front-side Bonding

2. Back-side bonding

3. Substrate Through via Bonding.

In this embodiment micro-devices may be of the same type or differenttypes in terms of functionality. In one embodiment, micro-devices aremicro-LEDs of the same color or of a number of different colors (e.g.,Red, Green, and Blue), and the system substrate is the backplane,controlling individual micro-LEDs. Such multi-color LED arrays arefabricated directly on a substrate or transferred to a temporarysubstrate from the growth substrate. In one example shown in FIG. 15,RGB micro-LED devices 1503, 1504, and 1505 were grown on asacrificial/buffer layer 1502 and the substrate 1501. In one case, thesystem substrate 1506 having contact pads 1507 can be aligned (FIG. 16)and bonded to the micro device substrate 1501 as shown in FIG. 17. Afterremoving the micro-device substrate 1501 (FIG. 18) andsacrificial/buffer layer 1502 (FIG. 19), a filler dielectric coating2001 (e.g., Polyimide resist) may be spin-coated/deposited on theintegrated sample (FIG. 20). This step may be followed by an etchingprocess to reveal the tops of the micro-LED devices. In the case ofmicro-LED devices, a common transparent electrode 2002 may be depositedon the sample. In another embodiment, a top electrode may be depositedand patterned to isolate micro devices for subsequent processes.

In another embodiment, as shown in FIG. 21 the micro devices 1503, 1504,and 1505 are grown on a buffer/sacrificial layer 1502. A dielectricfiller layer 2101 is deposited/spin-coated on the substrate to fullycover the micro devices. In one example illustrated in FIG. 21, thisstep is followed by an etching process to reveal the tops of the microdevices 1503, 1504, and 1505 to form the top common contact and seedinglayer for subsequent processes (e.g. electroplating). Referring to FIG.22, a thick mechanical supporting layer 2102 is then deposited, grown orbonded on the tops of the sample. Here, the filler layer 2101 can be ablack matrix layer or a reflective material. Also, before depositing themechanical support, one can deposit an electrode (either as a patternedor a common layer). The mechanical support layer is then deposited. Inthe case of optoelectronic devices such as LEDs, the mechanical supportlayer needs to be transparent. As shown in FIG. 23 and FIG. 24, themicro device substrate 1501 or sacrificial/buffer layer is then removedusing various processes such as laser lift-off or etching. In one case,the thickness of the substrate is initially reduced to a few micrometersby processes such as but not limited to deep reactive ion etching(DRIE). The remaining substrate then is removed by processes such as butnot limited to a wet chemical etching process. In this case, thebuffer/sacrificial layer 1502 may act as an etch-stop layer to ensure auniform etched sub-surface and to avoid any damage to the micro devices.After removing the buffer layer 1502 as shown in FIG. 24, anotheretching (e.g., RIE) is performed to expose the micro devices. One maydeposit and pattern a metallic layer to serve as the upper contact andbond pads for the micro-devices if they haven't been formed during themicro device fabrication. The system substrate 1506 having contact pads1507 can then be aligned and bonded to the micro device array as shownin FIG. 25. Depending on the type and functionality of the microdevices, the mechanical supporting layer 2102 and filler layer 2101 maybe then removed as shown in FIG. 26A and FIG. 26B.

In another embodiment, through substrate vias are implemented to makecontacts to the back of the micro devices.

Referring to FIG. 27, in one embodiment, the micro devices 1503, 1504,and 1505 may be multicolor micro-LEDs grown on an insulating bufferlayer 1502. This buffer layer may function as an etch-stop layer aswell. A dielectric layer 2701 is deposited as a filler layer.

Referring to FIG. 28A and FIG. 28B, using processes such as but notlimited to photolithography, patterns are formed on the backside of thesubstrate 1501. In one embodiment, a method such as DRIE is used to makethrough substrate holes in the substrate 1501. Buffer layer 1502 whichmay act as an etchstop layer may be removed using for example a wet-etchprocess, as illustrated in FIG. 28B.

Referring to FIG. 29, an insulating film 2901 is deposited on the backof the substrate 1501. This insulating layer 2901 may be partiallyremoved from back side of the micro devices 1503, 1504, and 1505 toallow formation of electrical contacts to these micro devices.

Referring to FIG. 30, the through holes are filled with a conductivematerial 3001 using processes such as but not limited to electroplating.Here, the vias may act as the micro device contacts and bonding pads.

As illustrated in FIG. 31, a common front contact 3101 of the microdevices 1503, 1504, and 1505 is formed by performing an etching process(e.g., using RIE) to reveal the tops of the micro-devices followed bythe deposition of a transparent conductive layer to form the frontcontact 3101.

Referring to FIG. 32, the micro device substrate 1501 is then alignedand bonded to the system substrate 1506 having contact pads 1507 whichin this example may be a backplane controlling individual devices.

In another embodiment, micro devices have been fabricated on a substratewith arbitrary pitch length to maximize the production yield. Forexample the micro devices may be multi-color micro-LEDs (e.g., RGB). Thesystem substrate for this example may be a display backplane withcontact pads having a pitch length different than those of themicro-LEDs.

Referring to FIG. 33A, in one embodiment, the donor substrate 1501 hasmicro device types 3301, 3302, and 3303 and they are patterned in theform of one dimensional arrays 3304 in which for each micro device 3301,3302, or 3303 from one type, there is at least a micro device fromanother type that their pitch 3305 matches the pitch of thecorresponding areas (or pads) on the receiver (or system) substrate.

As an example, in one embodiment shown in FIG. 33B, the pitch 3404 ofcontact pads 1507 is two times larger than the pitch 3402 of the microdevices 3401 as shown in FIG. 33.

Referring to FIG. 34, the system substrate 1506 and micro devicesubstrate 1501 are brought together, aligned and put in contact.

As shown in FIG. 35 and FIG. 36, methods such as laser lift-off (LLO)may be used to selectively transfer the micro devices 3401 to thecontact pads 3403 on the system substrate 1506. As shown in FIG. 37,transfer may be followed by depositing a filler layer 3701 and aconformal conductive layer 3702 on top of the system substrate as thecommon electrode.

In another embodiment shown in FIG. 38, a buffer layer 3801 is necessaryas a material template for the fabrication of micro devices 1503, 1504,and 1505.

Still referring to FIG. 38A and FIG. 38B, the buffer layer 3801 isdeposited on the sacrificial layer 1502 and patterned to isolate microdevices 1503, 1504, and 1505. In some cases, the sacrificial layer 1502may be patterned as well.

In one embodiment, instead of isolating individual micro devices, groupsof micro devices may be isolated from one another (as shown in FIG. 38)to facilitate the transfer process.

Referring to FIG. 39, a filling material 3901 such as but not limited topolyimide may be spin coated on the substrate to fill the gap betweenthe individual micro devices. This filling step insures the mechanicalstrength during the transfer process. This is particularly importantwhen a process like laser lift-off is used to detach micro devices fromthe carrier substrate.

Referring to FIG. 40, micro devices may not have the same height whichmake it difficult to bond them to the system substrate. In these cases,one can implement an electrostatic grip mechanism 4001 or other gripmechanisms in the system substrate to temporarily keep the micro deviceson the system substrate for the final bonding steps. The grip mechanismmay be local for micro devices or a global grip for a group of microdevices as in the case of same-pitch transfer for the whole wafer. Thegrip mechanism may be on a layer above the contact electrode. In thiscase, a planarization layer may be used.

In one embodiment, referring to FIG. 41A, the pattern of different microdevice types 3301, 3302, and 3303 on donor substrate create a twodimensional array of each type (for example array 4100) where the pitchbetween the arrays 4101 defined as the center-to-center distance betweenadjacent arrays) matches the pitch of the corresponding area on thesystem substrate.

In one embodiment shown in FIG. 41B and FIG. 42, when sub-device pitch4101 is larger than the normal distance between fabricated individualmicro devices on their substrate (e.g., in large displays), micro devicesubstrate 1501 is laid out in the form of two-dimensional single colorarrays. Here, the contact pad pitch 4102 and the micro device arraypitch 4103 are the same. Using this technique, one may relax the microdevice fabrication requirements and reduce the selective transferringprocess as compared to that described above.

FIG. 43 and FIG. 44 shows an alternative pattern where micro devices arenot formed in two-dimensional groups and the different micro devicesuniformly placed across the substrate as it shown in FIG. 43 for threedifferent micro devices.

Referring to FIG. 45, in another embodiment, micro devices are firsttransferred to a conductive semi-transparent common substrate 4501, thenthey are bonded to a system substrate 4502.

Color Conversion Structure

In some embodiments where the micro devices are optical devices such asLEDs, one can use either color conversion or color filters to definedifferent functionality (different colors in the case of pixels). Inthis embodiment, two or more contact pads on the system substrate arepopulated with the same type of optical device. Once in place, thedevices on the system substrates are then differentiated by differentcolor conversion layers.

Referring to FIG. 46A and FIG. 46B, in one embodiment, aftertransferring micro devices 1503 to the system substrate 1506, the wholestructure is covered by a planarization layer 4601. A common electrode4602 is then formed on the planarization layer 4601. The planarizationlayer can be the same height as, taller than, or shorter than thestacked devices. If the planarization layer is shorter (or there is noplanarization layer) the wall of the device can be conformally coveredby passivation materials.

Referring to FIG. 47, a bank structure 4701 is developed (especially ifa printing process is used to deposit the color conversion layers). Thebank can separate each pixel or just separate different color conversionmaterials 4702.

FIG. 48 shows an integrated structure where the color conversion layer4702 fully covers the top of the transferred micro devices and partiallycovers their sides. Bank 4701 separates the color conversion layers 4702and the electrode 4602 is a common contact for all transferred microdevices.

FIG. 49 shows an integrated structure where the color conversion layer4702 fully covers the top of the transferred micro devices and partiallycovers their sides. Bank 4701 separates the color conversion layers andcontacts to the micro devices are made only through the system substrate1506.

FIG. 50 shows an integrated structure where the color conversion layeris directly formed on the common electrode 4602. In this case no banklayer is used.

FIG. 51 shows an integrated structure where the color conversion layer4702 fully covers the top of the transferred micro devices and partiallycovers their sides. The electrode 4602 is a common contact for alltransferred micro devices. In this case no bank layer is used.

FIG. 52 shows an integrated structure where the color conversion layer4702 fully covers the top of the transferred micro devices and partiallycovers their sides. The contacts to the micro devices are made onlythrough the system substrate. In this case no bank layer is used.

In one embodiment, shown in FIG. 53A and FIG. 53B, after forming thecolor conversion material 4702 on the integrated system substrate 1506,a planarization layer 5301 is deposited on the structure. In some caseswhere the color conversion material and/or other components of theintegrated substrate need to be protected from environmental conditions,an encapsulation layer 5302 is formed over the whole structure. Itshould be noted that the encapsulation layer 5302 may be formed from astack of different layers to effectively protect the integratedsubstrate from environmental conditions

Referring to FIG. 54A and FIG. 54B, in another embodiment a separatesubstrate 5401 coated with the encapsulation layer 5302 may be bonded tothe integrated system substrate.

The embodiments depicted in FIG. 53 and FIG. 54 may be combined in whichencapsulation layer 5302 is formed both on the structure and theseparate substrate for more effective capsulation.

The common electrode is a transparent conductive layer deposited on thesubstrate in the form of a blanket. In one embodiment, this layer canact a planarization layer. In some embodiments, the thickness of thislayer is chosen to satisfy both optical and electrical requirements.

The distance between the optical devices may be chosen to be largeenough so as to reduce cross-talk between the optical devices or ablocking layer is deposited between the optical devices to achieve this.In one case, the planarization layer functions also as a blocking layer.

After the color conversion layers are deposited, different layers suchas polarizers can be deposited.

In another aspect, color filters are deposited on the color conversionlayers. In this case wider color gamut and higher efficiency may beachieved. One can use a planarization layer and/or bank layer after thecolor conversion layer before depositing the color filter layers.

The color filters can be larger than the color conversion layer to blockany light leakage. Moreover, a black matrix can be formed between thecolor conversion islands or color filters.

FIGS. 55A, 55B, and 55C illustrate structures where the device is sharedbetween a few pixels (or sub-pixels). Here the micro device 1503 is notfully patterned but the horizontal condition is engineered so that thecontacts 1507 define the area allocated to each pixel. FIG. 55A showsthe system substrate 1506 with contact pads 1507 and a donor substrate1501 with micro devices 1503. After the micro devices 1503 aretransferred to system substrate (shown in FIG. 55B), one can do postprocessing (FIG. 55C) such as depositing common electrode 4602, colorconversion layers 4702, color filters and so on. FIG. 55C shows oneexample of depositing color conversion layers 4702 on top of the microdevice 1503. However, the methods described in this disclosure and otherpossible method can be used.

It is possible to add the color conversion layers as described intopixel (or sub-pixel) active areas after formation of the active area.This can offer a higher fill factor and higher performance and alsoavoid color leaking from the side pixel (or sub-pixel) if the activearea of the pixel (or sub-pixel) is covered by reflective layers.

While particular implementations and applications of the presentdisclosure have been illustrated and described, it is to be understoodthat the present disclosure is not limited to the precise constructionand compositions disclosed herein and that various modifications,changes, and variations can be apparent from the foregoing descriptionswithout departing from the spirit and scope of an invention as definedin the appended claims.

What is claimed is:
 1. An integrated device comprising: a plurality ofpixels, each pixel comprising at least a micro device integrated on areceiver substrate; a patterned filler layer formed about a first microdevice of a first pixel, the patterned filler layer extending an activearea of the first pixel to an area larger than an area of the firstmicro device; and a sidewall reflective layer formed around thepatterned filler layer defining the first pixel.
 2. The integrateddevice according to claim 1, wherein the sidewall reflective layercovering at least a portion of one of: a top and a bottom of thepatterned filler layer and confining at least a portion of incoming oroutgoing light within the active area of the first pixel.
 3. Theintegrated device according to claim 2, wherein the sidewall reflectivelayer is fabricated as an electrode of the first micro device.
 4. Theintegrated device according to claim 1, wherein the patterned fillerlayer is further formed about a second micro device and between thefirst micro device and the second micro device of the first pixel. 5.The integrated device according to claim 1, wherein the patterned fillerlayer is comprised of a dielectric filler material.
 6. The integrateddevice according to claim 1, further comprising: a dielectric layerformed between the sidewall reflective layer and the patterned fillerlayer.
 7. The integrated device according to claim 1, furthercomprising; a transparent conductive layer formed over a top of thefirst micro device; and a contact pad formed at a bottom of the firstmicro device, wherein the contact pad is formed with a concave structurecapable of enhancing the outcoupling of light from the first microdevice.
 8. The integrated device according to claim 1, wherein thesidewall reflective layer is fabricated as a portion of the electrode ofthe first micro device.
 9. The integrated device according to claim 1,wherein the sidewall reflective layer is covered by a black matrix toreduce an ambient reflection of the integrated device.